Method op manufacturing pleated filters

ABSTRACT

A METHOD OF MANUFACTURING FLAT PLEATED FILTER ELEMENTS FOR FLUID SYSTEMS INCLUDING THE STEPS OF FORMING A FLUID PERVIOUS MATERIAL SUCH AS PERFORATED METAL OR THE LIKE INTO A PLURALITY OF PLEATS, OVERLAYING THE SURFACE OF THE PERFORATED MATERIAL WITH A SHEET OF NYLON, PROVIDING RODS AT THE INSIDE OF THE BENDS TO HOLD THE NYLON AGAINST THE PERFORATED MATERIAL AND THEN MOLDING (A THERMOSETTING) FRAME AROUND THE PERIPHERY OF NYLON AND PERFORATED MEMBER TO HOLD THESE MEMBERS TOGETHER.

Aug. 22, 1972 M Q RQSAEN ETAL Re.

METHOD OF MANUFACTURING PLEATED FILTERS Original Filed larch 7. 1966 2Sheets-Sheet 1 HI 1 INVENTORS 2 II V NILS o. ROSAEN some 0. ROSAEN///7./// oscAR E. ROSAEN 1 :75 Kil ATTORNEYS Aug. 22, 1972 M Q RQSAEN ETAL Re. 27,466

METHOD OF MANUFACTURING PLEATED FILTERS Original Filed March 7. 1966 2Sheets-Sheet 2 NILS O- ROSAEN BORJE O- ROSAEN OSCAR E. ROSAEN 1 /7/ATTORNEYS United States Patent 27,466 METHOD OF MANUFACTURING PLEATEDFILTERS Nils 0. Rosaen, Bloomfield Hills, Borje O. Rosaen, Ann

Arbor, and Oscar E. Rosaeu, Grosse Pointe, Micln, assignors to UniversalFilters, Inc., Hazel Park, Mich. Original No. 3,389,031, dated June 18,1968, Ser. No. 532,232, Mar. 7, 1966. Application for reissue Sept. 30,1969, Ser. No. 868,247

Int. Cl. B32b 31/16 US. Cl. 156-74 13 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE A method of manufacturing flat pleated filterelements for fluid systems including the steps of forming a fluidpervious material such as perforated metal or the like into a pluralityof pleats, overlaying the surface of the perforated material with asheet of nylon, providing rods at the inside of the bends to hold thenylon against the perforated material and then molding [a thermosetting]frame around the periphery of nylon and perforated member to hold thesemembers together.

The present invention relates to filters for fluid mediums and morespecifically to an improved method of fabricating pleated filters andadditionally to an improved filter formed in accodance with theaforementioned process.

Pleated filter elements are widely used in industrial applications forremoving foreign substances from fluid mediums such as air, andhydraulic and lubricating oil systems. Filters of this type areparticularly advantageous because of the large total area of filteringsurface that can be disposed in the path of the moving fluid.

Pleated filter units are customarily formed on a selfsustaining sheetfilter material formed into a plurality of relatively sharp edged ridgesconnected by folds. Because these sharp edged ridges are susceptible towear due to abrasion by foreign substances in the flowing mediumimpinging on the leading edges of the pleats, various methods have beendeveloped to extend the life of filters of this type such as by cappingthe leading and trailing edges of the pleats for the purpose ofincreasing the frontal area of these edges and also to strengthen theseareas that are generally weakened by folding.

In addition to the above problems, conventional pleated filters areusually made of a non-rigid filter material. The pleats of materials ofthis character tend to open and close under pulsating or irregular fluidpressures, sometimes to the extent of opening some pleats while closingothers. Because such filters are usually provided with a protectiveperforated sheet material or screen disposed adjacent the leading edgesof the pleats, these edges, due to flexing, tend to frictionally rubagainst the perforated shield thereby reducing the life of the filter.One solution to the above problem has been to positively anchor theedges of the pleats to the protective screen by capping the leading andtrailing edges of the pleats and then bonding these edges to theadjacent screen. It is apparent that this method of lengthening the lifeof pleated filters by capping the pleats in order to provide additionalstrength and increased frontal area and then bonding each of thesecapped edges to the adjacent screen involves a number of difficultmanufacturing steps.

One embodiment of the present invention solves the aforementionedproblems in addition to providing a num- "Ice her of special advantagesin manufacturing pleated filters by forming a pleated perforated backingplate having a fluid pervious material such as a nylon mesh imposed onone face. The backing plate is preferably formed of metal into two setsof substantially U-shaped opposed and staggered bends connected bysubstantially parallel folds. The nylon mesh is firmly held in place byinserting an elongated rod member into each of one set of U-shaped bendsso that the mesh is frictionally contained between the rods and thebends. The nylon mesh is formed with a lesser porosity than theperforated backing plate. The peripheral edge of the backing plate andnylon together with the ends of the rods are then imbedded in a plasticframe preferably of a thermosetting epoxy.

The framing step is dependent on the peripheral shape of the filterelement. A rectangular frame is preferably formed one side at a time. Amoulding container having interior cross-sectional dimensionssubstantially conforming to the desired frame side dimensions isprepared by coating the interior of the mold with a suitable partingagent such as the non-stick coating materials now available. A thinlayer of material such as a fluid thermosetting epoxy is poured in thebottom of the mold over which is laid a fiber-glass sheet. A second thinlayer of epoxy is poured over the sheet followed by a pair of parallelwire spacers. The fiberglass sheet and the wire spacers reinforce theframe to prevent cracking and insure that the edges of the filteringmaterial will not extend through the edges of the frame. The plate, meshand rods are then inserted in the mold followed by pouring a layer ofepoxy to a suitable depth to imbed the downwardly disposed frame side.The mold is capped and the mold and contents [are] then can be cured atroom temperature followed by heating in a curing oven for a timesufficient for the epoxy to assume a solid state. After cooling, theaforementioned process is repeated for each of the sides of the filterelement.

A circular frame is formed by inserting the plate and nylon mesh in asuitably prepared rotatable mold having a circular molding chamber andan open face. The mold is capped with a cover provided with a fluidconducting means adapted to deliver the epoxy adjacent the circular wallof the mold chamber. The mold container is rotated and the epoxy pouredtherein until the desired radial thickness has been obtained. The moldthen can continue [continues] to be rotated at room temperature and thenat an elevated temperature to cure the epoxy. When the epoxy has assumeda solid state, the mold continues to rotate to assist in cooling thecontents prior to removal.

By providing a rigid pleated backing plate having U- shaped bendssupporting the filtering material, the improved filter eliminates thenecessity for screens embracing the filter element as is utilized inconventional filters of this type. There are no sharp edge pleatsrequiring reinforcement or capping to obtain a suitable filter life. Byutilizing a nylon mesh, an improved filtering material has been providedwhich has not previously been readily adaptable to filters constructedusing conventional fabrieating methods. The plastic framing method notonly provides an improved non-corrosive frame but in addition, theaforementioned technique provides a relatively simple method for framinga unitary filter element.

It is therefore an object of the present invention to improve the methodof making pleated filters comprising the steps of pleating a metallicperforated backing plate, imposing a flexible fluid pervious materialagainst one perfortaed surface of the backing plate, and imbedding theperipheral edge of the backing plate and fluid pervious material in athermoseting plastic frame.

It is another object of the present invention to improve the filteringcharacteristics and life of pleated filter elements by providing such afilter comprising a pleated, perforated filter backing plate havingsubstantially U- shaped ridges connected by substantially parallelfolds, a nylon mesh filtering material imposed adjacent one surface ofthe backing plate, and a plastic frame enclosing the peripheral edges ofsaid plate and filter material.

It is still another object to improve the method of framing circularpleated filters comprising the steps of inserting the shaped filtermaterial in a mold having a circular chamber, rotating the mold, pouringa thermosetting epoxy adjacent the rotating interior circular wall ofthe mold to provide a circular frame enclosing the filter material, andheating the rotating mold and contents to assist the epoxy to assume asolid state.

Still further objects and advantages will readily occur to those skilledin the art upon reference to the following detailed description and theaccompanying drawings in which:

FIGS. l-4 are diagrammatic representations of successive stepsillustrating the improved method of producing pleated filters;

FIG. 5 is a perspective view of an improved filter made according to theimproved process with parts cut away for clarity;

FIG. 6 is a cross sectional view of an alternative embodimentillustrating the present invention;

FIG. 7 is a schematic representation of the heating and rotating stepsduring the production of a circular filter and with parts cut away andother parts removed for clarity; and

FIG. 8 is a cross sectional view taken substantially at line 88 of FIG.7.

Now considering first the method of the invention in some detail, andreferring to FIG. 1, the first step includes pleating a perforated,preferably metallic, material to form a rigid backing plate 10. Theplate 10 is formed into two sets of opposed and staggered U-shaped bendssuch as at 12 connected by substantially parallel folds 14.

A fluid pervious material 16 preferably of a nylon mesh and having aporosity less than the perforated plate 10 is then imposed over asurface of the plate 10 by inserting a plurality of rods 18, one rod ata time, into one set of U-shaped bends 12 so that the material 16 isintermediate the rod 18 and the bend 12. The rods 18 are formed ofsubstantially the same diameter as the bends 12.

Now referring to FIG. 2, the plate 10, material 16 and rods 18 are thendisposed intermediate a lower clamping member 20 and an upper clampingmember 22. A block 23 has a plurality of parallel spaced ribs 24 whichare forced downwardly over the rods 18 by tightening screws 26connecting the clamping members 20 and 22 so that the bends 12 fiexsufficiently to frictionally retain the rods 18 and the material 16tightly therebetween. It is to be understood that in the aforementionedstep, the material 16 is tightly drawn against the surface of the plate10 by the rods 18. For purposes of description, the plate 10 is formedwith a rectangular peripheral edge comprising four sides 28. Thematerial 16 is trimmed adjacent the sides 28.

Now referring to FIGS. 3 and 4, a frame 30 having opposite sides 32formed with inwardly disposed channels 34 is prepared by first coatingthe surfaces forming the channels 34 which a suitable parting agent suchas the nonstick materials now available. In one preferred method, a thinlayer 36 of a thermosetting plastic such as epoxy is poured into one ofthe channels 34 and a reinforcing material 38 such as fiberglass isdisposed over the layer 36. The material 38 is preferably formed withperipheral dimensions slightly less than the cross-section of thechannel 34. A second thin layer 40 of epoxy is then poured over thematerial 38-. A pair of spaced parallel thin elongated spacing rods 42are deposited on the layer 40. The opposite side 32 is then removed byremoving the screws 43 and the pleated assembly without the block 23 andthe clamping members 20, 22 but comprising the plate 10, the material 16and rods 18 is inserted in the frame 30 so that one side 28 rests on therods 42. The side 32 is mounted back in place and a third layer of epoxyis poured into the channel 34 to imbed the plate side 28 in a plasticframe side 46 as shown in FIG. 5 formed by the layers of epoxy, material38 and the rods 42.

The epoxy [is] can be cured at room temperature for approximately thirtyminutes and then the frame 30 and contents [are] can be deposited in abake oven 48 as shown in FIG. 4 and heated for a time sulficient for theepoxy to assume a solid state. A preferred curing time in the oven 48has been found to be approximately three hours at about ISO-200. Duringthe curing steps the reinforcing material 38 functions to prevent theplastic frame side 46 from cracking.

When the plastic side 46 has cooled, the aforementioned steps arerepeated to form the opposite side 46. The remaining sides are similarlyformed but without the spacing rods 4-2.

A completed filter element 47 as shown in FIG. 5 is then finished bycleaning the edges and sanding the top and bottom sides.

The provision of the material 38 and rods 42 is to strengthen the frameside 46 and also to insure that the edges of the plate 10 and thematerial 16 will not protrude through the exterior surface of the frameside 46. FIG. 4 illustrates another preferred method of forming theframe side 46 which does not require either the material 38 or the rods42. The vertically extending sides 35 of the frame 30 are provided withoutwardly extending dowels or pins 49 which engage one of the clampingmembers 20, 22 to maintain the lower edge of the pleated assemblyslightly above the bottom of the channel 34 during the steps illustratedin FIGS. 3-4. The layer of epoxy 40 is then poured to a depth to imbedthe side 28 in the plastic frame side 46. In this way, although somestrength is sacrificed, the edges of the plate 10 and the material willbe disposed inwardly of the exterior surface of the frame side 46 and anumber of steps in the process can be eliminated.

FIG. 6 illustrates the cross-section of an alternate embodiment of animproved rectangular filter in which a second elongated rod 52 similarto rod 18 is set in one side 46 to prevent warping and a rectangularplate 56 is set in the opposite side 46. The side 46 and plate 56 aretihen drilled and tapped as at 60 to accommodate a han- FIGS. 7-8schematically illustrate a method of producing a circular filter 64. Thepreliminary steps are similar to the aforementioned steps for formingthe rectangular filter 47. A perforated backing plate 60 is pleated withU-shaped bends 62 and substantially parallel folds 64. A fluid perviousmaterial 66 is disposed adjacent a surface of the plate 60. The material66 has a lesser porosity than the perforated backing plate 60. However,to eliminate the necessity of utilizing retaining rods of varyinglengths to serve the function of the rods 18 as in the rectangularfilter method, corrugated spacers 67 are inserted interjacent each ofthe parallel folds 64 to position the fluid pervious material 66 againstthe pleated surface of the plate 60 and to maintain the spacing betweenthe plates. The pleated assembly is then cut to a circular shape and thepleated plate 60, material 66 and spacers 67 are then inserted in arotatable container 68 having an open faced non-stick material coatedcircular chamber 70. An annular spacer plate 74 is disposed in thecontainer 68 and has a plurality of parallel rows of projecting guideposts 76 which are adapted to extend through the spacers 67 to rigidlylocate the perforated plate 60 in the chamber I0 during the frameforming operation. A fixture 77 is mounted over the open side of theassembly and is provided with pins 79 extending through the spacers 67and into the pleats to aid in maintaining the assembly in position withthe proper spacing between the pleats. A cover 78 having afrusto-conical central portion 80 and a central opening 82 is attachedto the container 68.

As shown in FIGURE 7, the container 68 is rotated by suitable means (notshown), and the epoxy is supplied to the chamber 70 through the opening82 so that it moves by centrifugal force to the outer edges of thecontainer 68 to form a circular filter frame '88 of a radial thicknesssuflicient to imbed the peripheral edges of the plate 60 and material66.

The frame 88 [is] can be cured at room temperature in the rotatingcontainer 68 for approximately one hour, then cured at an elevatedtemperature by heating lamps 90 or any other suitable heating means forapproximately three hours until the epoxy has assumed a solid state. Therotating step continues for approximately one hour to allow the frame 88to cool. During the cooling step, the frame 88 will experience a slightshrinkage so that it is readily removable from the container 68. Thecircular filter 64 is then finished by removing the plate 74 and thefixture 77, smoothing the corners and sanding the faces.

It can therefore be seen from the foregoing description that we havedisclosed an improved method of making pleated filters, eitherrectangular or round. By utilizing a nylon mesh backed by a pleated,metallic, rigid backing plate, the screens required in conventional typefilters have been eliminated in addition to utilizing an improvedfiltering material. By imbedding the filter edges in a [thermosetting]plastic material, a simpler framing method has been disclosed whichproduces an improved long lived non-corrosive frame. Furthermore, byforming a rigid pleated filter element having U-shaped leading andtrailing edges rather than the relatively sharp edges of conventionalfilters, the requirement for capping such edges to resist abrasion fromforeign substances in the fluid medium has been eliminated, therebypermitting an improved filter having a greatly increased efliciency andan increased useful life to be produced in a relatively few fabricatingsteps.

It is to be understood that although we have disclosed an improvedmethod for producing rectangular and circular filters, the essence ofthe invention can be utilized to produce filters having a variety ofirregularly shaped frames.

It has been found that a preferred thermosetting epoxy is a commerciallyavailable material marketed under the trade name MARASET" comprising 644F-2 Resin Epoxy with #75 Hardener by Marblette Corporation, Long Island,NY.

While it has been preferred to describe the filter ele ments of thepresent invention as including perforated sheets and material such asnylon, it is to be understood that these can be replaced by a singlesheet of perforated material if this is desired. For example the backingsheet could be used alone to act as a filtering medium.

Further, if so desired, the epoxy which is used for the frames can bereplaced by other suitable [thermosetting] materials and for strengthcan comprise an epoxy provided with a filler of metallic powders.

It is to be understood that although we have described a preferredmethod for producing several embodiments of our invention, variouschanges and modifications couid be made without departing from thespirit of the invention as expressed by the scope of the appendedclaims.

We claim:

1. A method of manufacturing a flat pleated filter element comprisingthe steps of:

(a) pleating a sheet of fluid pervious material to form a plurality ofbends connected by folds, (b) shaping said pleated sheet in the form ofa circle, (c) inserting said sheet in a rotatable container having acircular chamber substantially complementarily shaped to said pleatedsheet, (d) rotating said container, (e) delivering a fluid thermosettingmaterial into said rotating container for a time and of an amountsuflicient for a circumferential layer of said thermosetting material toenclose the peripheral edge of said sheet, and

(f) heating said rotating container and the contents thereof for a timeand at a temperature sufiicient for said thermosetting material toassume a solid state.

2. The method as defined in claim 1 and including the step of insertingcorrugated spacers interjacent parallel folds of the pleated sheet priorto inserting said sheet in said rotatable container.

3. The method as defined in claim 1 and including the step of mounting afixture on one side of the pleated sheet with pins extending into thepleats to aid in maintaining the spacing between the pleats while thesheet is being inserted in the rotatable container and during forming ofthe layer about the peripheral edge of the sheet.

4. A method of forming a flat, pleated filter element comprising thesteps of (a) pleating a sheet of rigid fluid pervious material to form aplurality of bends connected by folds,

(b) imposing a second sheet of material of less porosity and moreflexible than said first mentioned sheet of material over the firstmentioned sheet,

(c) inserting a fixture over said sheets which also has means extendingwithin adjacent pleats of said sheets for maintaining said sheets withtheir surfaces adjacent so that both sheets form a pleated assembly,

(d) placing said pleated assembly and fixture in a mold and molding aframe of thermosetting plastic material around the perimeter of saidpleated as sembly, and

(e) removing said fixture only after said frame has been formed.

5. The method as defined in claim 4 and including the steps of:

(a) placing rods intermediate the extending means of said fixture andsaid pleated assembly,

(b) forming said rods of a diameter slightly greater than the curvatureof the bends forming the pleats in said pleated assembly whereby uponsaid rods being forced into the pleats by said fixture they will befrictionally retained in place.

6. A method of manufacturing a flat, pleated filter element comprisingthe steps of:

pleating a sheet of fluid pervious material to form a plurality of bendsconnected by folds,

inserting said sheet in a rotatable container having a chambersubstantially complementarily shaped to said pleated sheer,

rotating said container,

delivering a plastic material into said rotating container for a timeand of an amount sufiicient for a circumferential layer of said fluidmaterial to enclose the peripheral edge of said sheet, and

rotating said container and the contents thereof for a time sufiicien!for said fluid material to assume a solid state.

7. The method as defined in claim 6 and including the step of insertingcorrugated spacers interjacenr parallel folds of the pleated sheer priorto inserting said sheet in said rotatable container.

8. The method of claim 7 and including the step of imposing a secondsheet of material of less porosity and more flexible than said firstmentioned sheet of material over the first mentioned sheet on the someside thereof as said corrugated spacers are inserted prior to insertingsaid corrugated spacers.

9. The method as defined in claim 6 and including the step of mounting afixture on one side of the pleated sheet with pins extending into thepleats to aid in maintaining the spacing between the pleats while thesheet is being inserted in the rotatable container and during forming ofthe layer about the peripheral edge of the sheet.

10. A method of forming a flat, pleated filter element comprising thesteps of:

pleating a sheet of rigid fluid pervious material to form a plurality ofbends connected by folds, imposing a second sheet of material of lessporosity and more flexible than said first mentioned sheet of materialover the first mentioned sheet, inserting a fixture over said sheetswhich also has means extending within adjacent pleats of said sheets formaintaining said sheets with their surfaces ad- ,iacent so that bothsheets form a pleated assembly, placing said pleated assembly andfixture in a mold and molding a frame around the perimeter of saidpleated assembly, and removing said fixture only after said frame hasbeen formed. 11. The method as defined in claim and including the stepsof:

placing rods intermediate the extending means of said fixture and saidpleated assembly, forming said rods of a diameter slightly greater thanthe curvature of the bends forming the pleats in said pleated assemblywhereby upon said rods being forced into the pleats by said fixture theywill be frictionally retained in place. 12. A method of forming a flat,pleated filter element comprising the steps of:

pleating a sheet of rigid fluid previous material to form a plurality ofbends connected by folds, imposing a second sheet of material of lessporosity and more flexible than said first mentioned sheet of materialover the first mentioned sheet, placing rods within pleats adjacent saidsecond sheet of material for maintaining said sheets with their surfacesadjacent so that both sheets form a pleated assembly, placing saidpleated assembly in a mold and molding a frame around the perimeter ofsaid pleated assembly. 13. A method of manufacturing a flat, pleatedfilter element comprising the steps of:

pleating a sheet of fluid pervious material to form a plurality of bendsconnected by folds,

inserting said sheet in a rotatable container having a chambersubstantially complementarily shaped to said pleated sheet,

molding a frame around the periphery of said sheet by inserting saidsheet in a rotatable container having a chamber substantiallycomplementarily shaped to said pleated sheet, and by delivering theframe material in a fluid state into said rotating container for a timeand of an amount suflic'ient for a circumferential layer of said fluidmaterial to enclose the peripheral edges of said sheet, and rotatingsaid container and the contents thereof for a time suffieient for saidfluid material to assume a solid state.

References Cited The following references, cited by the Examiner, are ofrecord in the printed file of this patent or the original patent.

UNITED STATES PATENTS 2,070,699 2/1961 Leuthesser ct a1. 210-4933,144,315 8/1964 Hunn -521 3,177,637 4/1965 Davis 55--521 3,246,457 4/1966 Debaun 55521 3,308,958 3/1967 Berger et a1. 210-493 FOREIGN PATENTS599,661 6/1960 Canada. 1,160,074 7/ 1958 France.

6,769 3/1902 Great Britain. 680,211 10/ 1952 Great Britain. 750,0996/1956 Great Britain. 806,109 12/1958 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner G. E. MONTONE, Assistant ExaminerU.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 6 DatedAugust 22 1972 Inventor(s) ilS O Rosaen et al It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 1, line 33, "accodance" should be --accordance.

Column 2, line 17, "moulding" should be molding.

Column 2, line 68, "perfortated" should be --perforated.

Column 2, line 70, "thermoseting" should be thermosettinq-- Column 3,line 63, "which" should be -with.

Column 7, line 30, delete "previous" and insert --pervious.

Signed and sealed this 15th day of May 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOT'ISCHALK Attesting Officer Commissionerof Patents 4 30-1050 (10-69, USCOMM-DC 60376-F'69 U 5 GQVERNMENTPRINTING OFFICF mnq n nnnnn u

